We caught up with Sallie Krawcheck after she sat on a panel at the Bloomberg Markets 50 conference.

The title of her panel was 'Fixing Broken Banks', but that's not the only thing that's keeping people up at night. There's a little continent on the other side of the Atlantic that's occupying their minds as well.

So we asked her about both of those.

Krawcheck told us that in terms of the banking system, her greatest fear is "fear of the unknown." To paraphrase, think: Knight Capital, The London Whale, LIBOR. It seems like there's always a terrible new story no one anticipated.

And the unknown, as you know, is limitless, so we don't know what risk lies within our complicated banking system. Yikes.

As for Europe, Krawcheck built us a nice metaphor. Where we are now, is "just a...lull on the rollercoaster." It's only a matter of time before we go through another loop.

Maybe some people are convinced that it's all over, "but I doubt it," she said.